I am going to discount the first so let us focus on the second as that provides the kind of criteria we can apply logic to and most people will relate to it. Body type is important because it comes with natural advantages and limitations which we usually cannot easily change. Doing any martial art is hard enough without battling our own body every step of the way so let’s go and see what we should be considering while we choose.
Body weight
Body weight in its own right is important, just as size is. While in every martial art you learn techniques which help you take down a bigger, stronger opponent, size and weight are natural advantages which are hard to overcome. If you are lucky enough to be tall and heavy or even medium-sized and heavy then you should consider going for a martial art which allows you to naturally use this in your favour. Judo and Aikido, martial arts which rely on body weight, grapples, joint locks and throws are perfect examples of this. Some of the soft Kung Fu styles such as Wing Chun are also great.
Flexibility
Again, every martial art tries to teach you to be more agile on your feet and become more flexible but it pays to make use of our natural ability anyway. If you do have a degree of natural flexibility or if you find it easy to do flexibility exercises you should consider a martial art like Tae Kwon Do, Shaolin Kung Fu or Kick Boxing. StrengthThrough training you are going to get stronger anyway, but if you can put on muscle easily Karate, Kick Boxing and any of the hard Kung Fu styles would be perfect for you.
Aims and intent
By choosing your body type as your main criteria you can certainly begin to narrow down the choices of martial arts available to you. It is also good to take into account your aim and intent. If you want something which, for instance, will help you keep fit, a recreational style Kick Boxing class is perfect because it is high-energy, dynamic and non-competitive. Self-defence is the inevitable by-product of every martial art but some help you do it better than others. Karate, Tae Kwon Do and Kick Boxing tend to be particularly good at providing you with the right first-hand resources for defending yourself. If you are looking for an outlet for your energy but do not want anything too competitive then Aikido and Judo are perfect offering a balanced mix of theory and practise.
Before you choose
It is fine to start off with a list of criteria which will help you narrow down your choice of martial art but nothing beats going to a class and taking part to see if it fits.
Most martial arts will allow you to participate in an obligation-free trial. This will allow you to see if the martial arts style, style of teaching, club atmosphere and mix of personalities really suit you or not. Then you can make an informed decision.